Hydraulic transmission



Nov. 1, 1927.

w. FERRls HYDRAULIC TRANSMI S S I 0N I N VEN TOR.

WH Tfn FERR/.s

A TTORNE Y.

Nov. 1, 1927.

W. FERRIS HYDRAULIC TRANSMISSION Original Filed Oct.26. 1922 6Sheets-Sheet 5 INVENTOR.

Wfl/ TER ERR/' ATTORNEY.

. 1922 6 Sheets-Sheet '4 Nov. 1, 1927.

W. FERRIS HYDRAULIC TRANSMISSION Original Filed 0011.26

I N VEN TOR.

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W. FERRIS HYDRAULIC TRANSMISSION Original Filed 0ct.26, 1922 6Sheets-Sheet 6 INVEN TOR. WqzTfA FERR/s ATTORNEY.

Patented Nov. 1, 1927.

UNITED STATES PATENT OFFICE.

WALTER FERRIS, OF MILWAUKEE, WISCONSIN', ASSIGNOR TO TE OILGEAR COMPANY,OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

HYDRAULIC TRANSMISSION.

Original application led October 26, 192.2, Serial No. 596,967. Dividedand this application led September 17, 1923. Serial No. 663,215.

This invention relates to hydraulic transmission mechanisms for use,primarily, wlth machine tools and the like, although certain novelfeatures thereof may be advantageously employed in other rela-tions.

One object of the present invention 1s the provision of novel meanswhereby the hydraulic transmission may be placed under the control ofthe part driven thereby. Means of the character referred to ma be usedto particular advantage in mac ine tools and the like, wherein it isdesirable for the tool or other driven part to automatically perform apredetermined cycle or move a predetermined distance and then come torest.

Some diiiiculty has been experienced in the application of hydraulictransmissions to some types of machines because of the'tendency of thedriven part to creep in one direc, tion or another when the pump issupposedlyT set at zero stroke. This results from the fact that inordinary practice it is extremely diflicult to set the pump at zerostroke -with thc extreme accuracy required. Another object of thepresent invention is to overcome this difficulty, and to this endprovision is made to automatically short circuit the high and lowpressure sides of the transmission system when the pump controlmechanism is in zero stroke position. y

Another object. is the provision of. improved protective devicesforhydraulic transmission systems by which undue pressures therein will beavoided.

Another -objeo't is the provision of improved control mechanism forhydraulic transmission systems.

Otjher objects and advantages will herein-v after' appear.

This application is a division of my copending application, Serial`No.596,967, filed October 26, 1922, which has matured into Patent No.1,468,595, issued the 18th day of September, 1923. Although thelhydraulic` transmission. mechanism is well adapted for and is hereinshown applied to a broaching machine, it will Vbe understood that it isalso well adapted for various other uses.

The figures of the drawings are as follows:

Figure 1 is a side elevation, partly in section, of a portion of abroaching machine having applied thereto a hydraulic transmissionconstructed in accordance with the present invention.

Figure 2 is a side elevation, partly in section, of the remainder of themachine.

Figure 3 is a plan view of that portion of the machine illustrated inFigure 1.

Figure 4 is a plan view of that portion of the machine illustrated inFigure 2.

Figure 5 is an axial sectional view of a variable displacement pumpconstituting a part of the hydraulic transmission.

Figure 6 is a sectional view taken substantially on the lipe6-6 ofFigure 5.

Figure 7 is a detail of a portion of the control mechanism.y

Figure 8 is a fragmentary plan View of the pump casing illustrating theapplication of another portion of the control mechanism thereto.

Figure 9 is a sectional View of a high pressure relief mechanismemployed for protecting the hydraulic system. A.

Figure 10 is a sectional view of a relief Valve constituting a part ofthe relief mechamsm.

lThe. broaching machine selected for illustration comprises a bed ortrough 10 of well known form provided at one end with 'the usual faceplate 11 through which-the broaching tool travels during its workingand'return strokes. A working cylinder 12 is arranged at the other end ofAthe trough and extends substantially in alignment therewith. Thiscylinder is preferably securely united with the trough 'through fourheavy tension rods 14, so that the two together form a substantiallyrigid structure supported intermediate its ends upon a heavy pedestal15.

A tool actuating cross-head 16 is mounted for reclprocation in the usualmanner between a pair of uides 17 extending within ,and longitudinal yofthe trough 10. The cross-head 16 is actuated by an appropriatehydraulic motgr which, in this instance, comprises the main cylinder 12hereinabove mentloned and an auxiliary cylinder 18. A piston 19reciprocable in the main vcylinder 12 and a iston 20 in the auxiliarycylinder 18 are bot connected with the cross-head 16 throughtheir-respective piston rods 21 and 22. The main plston rod 21 isconnected with the cross-head justhbelow the usual tool receiving socket23 and the auxiliary ist rod .'22 above the socket at a somewhat greaterdistance therefrom. ln fact, the distance of each piston rod from thesocket is preferably inversely proportional to the effective pull of therespective rods, so that there is no tendency for the cross-head to rockor bind upon its guides as the broaching tool is being pulled throughthe work.

The opposite ends of the cylinder 12 are in direct communication,through pipes 24 and 25, respectively, with the two sides of thehydraulic circuit established by the pump 26, a port 27 effectingcommunication between one end of the cylinder 12 and the correspondingend 28 of the cylinder 18. The volumetric capacity of the end 28 ofcylinder 18 is preferably substantially equal to the volumetricdisplacement of the piston rod 21 within'the cylinder 12, so that therate of flow of the liquid in the one pipe 24 is always equal to that inthe other pipe 25. Tn other words, as the pistons 19 and 20 movesimultaneously toward the right, the volume of liquid discharged fromthe right "end of cylinder 12 is equal to the total volume of liquidadmitted to the left ends of cylinders 12 and 18. The same volumetricrelation exists when the pistons 19 and 20 move toward the left. Thus,it will be noted that the volumetric capacity of the entire hydraulicsystem remains constant notwithstanding the dierential capacities of thetwo ends of the cylinder 12 resulting from the displacement of thepiston rod 21. The inactive end of the auxiliary cylinder 18communicates through a pipe 29 with the base of the pump casing intowhich any leakage past the piston 18 may be .discharged.

The machine illustrated is of that type in which the broaching tool ispulled through the work, so that to perform a working stroke uliquid isdelivered into the leftends of the cylinders 12 and 18 through the pipe24 and to effect al return stroke liquid lis forced into the right endof the cylinder 12 through the pipe 25. To obtain a steady advance ofthe toolr it is essential that the driving liquid be supplied at asteady rate rather than under a constant pressure. This is accomplishedin this `instance by directly connecting to the pipes 24 and 25 a pump26, capable of delivering a steady iiow of liquid to either inaccordance with the direction of the stroke desired. The pump 26 hereinemployed is a reversible, constant speed, variable displacement pump ofthe type fully described in my copending application Serial No. 483,468,filed July 9, 1921.

This pump, as shown in Figures 5 and 6, comprises a casing' 30 having apintle 31 rigidly secured therein. The pintle 'contains two pairs ofducts 32 and 33,' one pair 32- such that when the pilot valve 55 isshifted communicating withv the pipe 24, the other pair with the pipe25. A cylinder barrel 34,-

mounted for rotation upon the pintle 31, is provided with a series ofcylinders 35 arranged in pairs and radially disposed with respect to thecenter of rotation. Each cylinder has a port 36 which is brought intocommunication with one or the other pair of ducts 32 and 33 duringrotation of the c linder barrel. A piston 37 is mounted .forreciprocation in each cylinder, each pair of pistons being integrallyconnected with a cross-head 38 which bears against a reaction plate 39removably secured in the periphery of a rotatable impelling ring 40.Appropriate anti-friction means 41 is interposed between each cross-head38 and its corresponding reaction plate 39 in order to permit freelateral movement therebetween.

The impelling ring 40 is journaled in bearlngs 42 and 43 in a cradle 44mounted to rock about a pintle 45 secured'within the lower partof thecasing 30 below the pintle 31. Rotation of the impelling ring 40 iseffected through a drive shaft 46 keyed thereto and extending outside ofthe pump casing. In this instance, the free end of the shaft 46 is shownprovided with a pulley 47 through which it is driven from a constantspeed motor 48, mounted upon a bracket 49 carried by the pedestal 15.This pump is fully described in the copending application hereinabovelast referred to so that a further detailed description thereof isdeemed unnecessary. Suffice it to say that when the cradle 44 is in anintermediate position so that the impelling ring is concentric with thepintle 31, rotation of the impelling ring will cause the pistons 37 totravel about the pintle 31 without reciprocation within their respectivecyli-nders 35. In this position, no liquid is delivered by the pump. Byrocking the cradle in one direction or another from a neutral position,the impelling ring will be made to assume an eccentric position and byits rotation cause a reciprocation of the pistons within theircylinders, thus causing the pump to produce a steady flow of liquid inopposite directions through the pairs of ducts 32 and 33 at a rate andin a .direction dependent upon the extent and direction of eccentricityof the impelling rin The cradle 44 is actuated an controlled bymechanism of the type disclosed in the copending application last aboveidentified. This mechanism includes a plunger 50 connected throughlinks51 with the upper end of the cradle 44,y as indicated at 52. Theplunger 5() is actuated by -a4 iston 53 mountu ed in a cylinder 54within t e pump casing.

= Movement of the piston 53 is controlled by a 'pilot valve 55reciprocally mounted within the plunger 50, and provided with .a valvestem 56 extending longitudinally of and beyond the plunger. Thearrangement is in either direction, Huid pressure is applied to one orthe other side of the piston 53 to cause the `plunger 50 and cradle 44to shift in a corresponding direction to an extent dependent upon theextent of movement of the pilot valve.

'end of the lever is pivotally connected at 6() with a centering plunger61, which tends at .alltimes tomamtain the lever 58 in a'neutralposition, that is, in such position that the stem 56, plunger 50and cradle 44 are in a neutral position and the impelling ringconsequently in concentric relation to the pintle 31. This isaccomplished by the use of a coiled sprincr 62 which normally bears atits opposite ends against collars 53 and 64 on the plunger 61, and whichis confined between one end 65 of a cylinder 66 and a shoulder 67therein. The plunger 61 is thus yieldably retained in an intermediateposition but is shiftable in either direction against the pressure ofthe spring.

The lever 58 is shiftable in either direction from the neutral positionby a plunger 68 actuated by mechanism to be hereinafter described. Thisplunger 68 is slotted or notched, as indicated at 69, to loosely embracea pin 70 secured tothe lever 58. This plunger is mounted forreciprocation in a valve chest 7l having two chambers 72 and 73 normallyin communication through a. port 74. Chamber 72 is connected through apipe 75 with the pipe 24 constituting one side of the hydraulic circuitand chamber 73 is connected through a pipe 76 with the pipe 25constituting the other side of the circuit.

'The plunger 68 is provided with a reduced portion 7 7 of smallerdiameter than the port 74 and so arranged as to permit a free flow ofliquid between the chambers 72 and 73 when the plunger 68 is in neutralposition. Thus, when the parts of the pump and pump control mechanismsare substantially in neutral position, the port 74 constitutes a by-passbetween the two sides of the circuit to insure against a building up ofpressure in the system which might otherwise result, due to a minuteeccentricity of the mpelling rin j. As the plunger 68 is shifted ineither irec-tion, however, one of the shoulders 78 or 79 thereof entersthe port 74 and shuts ofi' communication between the chambers 72 and 73and the by-pass is destroyed. The loose play betweenl the notch 69 ofthe plunger 68 and the pin 70 on the lever 58 is preferably suchas ltopermit the shifting of the plunger 68 into ort closing position beforethe lever 58 is shifted from neutral position. Further movement of theplunger 68 then causes a corresponding shiftm of the lever 58 to theextent desired.

In t e machine shown, the plunger 68 1s connected at 68 ywith a link 80connected with and actuated by an arm 80 constituting a part of apivoted bracket 8l mounted upon a fixed bracket 82 so as to rock about asubstantially vertical axis. Bracket 82 is secured by U-bolts 83 to apair of tension rods 14 hereinabove referred to. Adjustable set screws84 and 85 carried by the pivoted bracket 8l limit the rocking movementof this bracket by their engagement with the vertical face of the fixedbracket 82. By an adjustment of either of these set screws the extent ofmovement of the bracket 8 1, and consequently the link 80, in eitherdirection, is nicely controlled. A spring pressedf latch pin 86,reciprocally mounted in a hollow lug 87 on the fixed bracket 82, isadapted to releasably retain the pivoted bracket 81 and lconsequentlythe link 80 in an intermediate or neutral position, by its engagement ina socket 88 formed in a sector 89 constituting a part of the pivotedbracket. -The pin 86 may be withdrawn from latching position through alink 90 by mechanism to be later described.

The pivoted bracket 81 is secured to a vertical shaft 91 journaled inbearings 92 in t-he fixed brackets, .and providedat its upper end withan arm 93 fixed thereto. Arm 93 is connected through a spring 94 with adetent rod 95, mounted for longitudinal reciprocation in guide brackets96 fixed to one side of thc trough l0 of the machine. A pair of lugs 97and 98, adjustably fixed to the rod 95, project into the path ofmovement of the tool actuating cross-head 16, and, throu h the rod 95,serve to automatically limit t e extent of movement of the cross-head ina manner to be now explained.

Assume that the parts are in the position shown in Figures 3 and v4 withthe detent rod in its right hand limiting position so that the spring 94tends to swing the arm 93 toward the right. The pivoted bracket isretained in its neutral intermediate position by the latch pin 86. Toinitiate the movement of the cross-head 16 the latch pin 86 is withdrawnby pulling the link 90. As soon as released the .pivoted bracket 8l isrocked in a clockwise direction, by the tension of the spring 94 uponthe arm 93, into its limiting position as determined by the setting ofthe screw 85. This results in the shifting of theflink 8() and. plunger68 in such direction as to cause the pump 26 to deliver liquid throughthe pipe 25 to the right end of cylinder 12. This causes an advance ofthe piston 19 and cross-head 16 to the left. This movement of thecross-head continues until the detent Irod 95 has been shifted towardthe left, by the engagement of the cross-head with the lug 97, and thespring 94 has been correspondingl shifted to cause the arm 93-to swingtowar the left. This obviously causes the pivoted bracket 81 lll) latchpin 85. The pivoted bracket, and con.

sequcntly the link 80 and plunger 68, have thus been returned to theneutral position .in which no liquid is delivered by the pump.

The cross-head 16 discontinues its advance and remains at this conditionof rest until the latch pin 86 has again been released by pulling thelink 90.

Movement of the cross-head 16 in the other direction is accomplished ina similar manner by withdrawing the latch pin 86. The detent rod 95 is,of course, in its extreme left hand position, so that the spring 94 isin such position as to pull the arm 93 toward the left when the socket,88"in the pivoted bracket is released. This results in a rocking of thepivoted bracket in a counter-clockwise direction, to a limiting positionas determined by the screw 84, and a corresponding shifting of the link80 and plunger 68 so as to cause the pump to deliver liquid through thepipe 24. As the liquid is forced into the left ends of cylinders 12 and18, the pistons 19 and 21, and consequently the cross-head 16, advancetoward the right until the detent rod 95 has been returned approximatelyto the position of Figure 3 by the engagement of the cross-head with thelug 98. When this occurs, the spring 94 is again in such position as totswing the arm 93 and the pivoted bracket in a clockwise direction untilrestrained by the latch pin in the neutral position. The pump is thusreturned to neutral and the cross-head brought to rest, in whichcondition it remains until the pin is again Withdrawn.

'l`hus,it will be noted that in the machine illustrated, mechanism isprovided for automatically limiting the extent of movement of thecross-head and tool and for retaining the crofgs-head at rest at eitherend of its stroke. This allows the operator ample time in which toremove or replace the tool or the work at either end of the stroke. ltwill be further noted that the extent of movement ofthe pivoted bracket,link 80iand plunger 68 in either direction is adjustable so that thepump displacement and consequently the rate of travel of the cross-headin either d1- rection may be varied to meet the conditions required.Thus the return stroke of the cross-head may be at a higher rate oftravel than the working stroke with a consequent saving of time betweenworking strokes.

Mechanism is also preferably provided by which the operator mayinterrupt or reverse the direction of travel of the cross-head at anypoint desired. In the machine shown, this mechanism comprises a handlever 99 conveniently mounted uponl a iixed pivot 100 at the side of thetrough 10. A depending arm 101, lixed to the hand lever 99, is connectedto one end of a link 102 which extends mame@ longitudinally of themachine and provided at its other end with a slot 103 embracing a stud104 carried by the pivoted bracket 81..4

The slot 103 permits the above described automatic rocking of thebracket 81 without disturbing the position of the lever 99 or link 102when these parts are in the intermediate position normally maintained bya pair of tension springs 104 fixed to the machine frame and to theopposite sides of lever 99.

A control rod 105 having a convenient button 106 is mounted upon thelever 99 for reciprocation lengthwise thereof. This rod is connectedwith one arm 107 of a bellcrank at a point 108 substantially concentricwith the rocking axis of the lever. The bellcrank is mounted to rockabout a pivot 109 fixed to the machine and its other arm 110 isconnected with the link 90 above referred to. rlhe arrangement is suchthat when the control rod 105 is depressed, the bellcrank is rocked insuch direction as to shift the link 90 and thus release the pivotedbracket 81 so as to start the cross-head on its working or return`strokes in the manner above described..

To arrest the movement of the cross-head it is only necessary to rockthe hand lever 99 'into such position as to shift the pivoted bracket8l-into neutral position by the action of the link 102. The bracket 81will normally be retained in this position by the latch pin 86 and thecross-head will come to and remain at rest. To effect reversal of thecross-head at any point in its travel,-the control rod 105 is depressedand -retained in a depressed condition by the thumb of the operator andthe hand lever is shifted sutliciently to reverse the position of thepivoted bracket `81.` Upon release of the hand lever and control rod7the pivoted bracket will automatically return to its neutral positionunder the action of spring 94 and the crosshead-.will come to rest.

Provision is also preferably made for guarding against undue pressure inthe hydraulic circuitto thus avoid injury to the tool or machine parts.In the machine shown, this is accomplished by the use of a hydrauliccircuit breaker by which a by-pass may be automatically establishedbetween the two sid/es of the circuit by pressures exceeding apredetermined limit. The circuit breaker shown comprises a valve chest111 having chambers 112 and 113 therein and a port 114 therebetween.Chamber 112 communicates with pipe 24 through a pipe 115 while chamber118 communicates with pipe 25 through a pipe 116. A balanced pistonvalve having three piston heads 117, 118 and 119 is reciprocally mountedwithin the valve chest. In its normal position, the piston head 118 isin the position shown within and closing the port 1-14 betweenthechambers. The three piston heads are of the same diameter so thatdifferences in pressure within the two chambers 112 and 113 will notaiect the normal position of the piston. One end of this piston isprovided with a stem 120 extending through the end wall of the valvechest by which the piston may be manually manipulated. A. spring pressedlatch 121, engageable in a groove 122 in the stem 120, tends to maintainthe piston in normal position. The opposite ends of the valve chest areprovided with bleeds 123 through which any accumulation of liquidtherein may drain off slowly through a discharge pipe 124 to the base ofthe pump casing.

Pressure relief valves 125 and 126 communicate with the pipes 115and'116, respectively, through plpes 127 and 128. Each relief valvecomprises a spring loaded valve 129 mounted ina chamber 130 andcooperatin with a valve seat 131 to normally pre-vent a ow of liquidfrom the pipe 127 or 128 into the chamber 130. 'Ihe tension in eachspring 132 may be varied and controlled by the usual pressure screw 133.The chambers 130 of the relief valves communicate through a pipe 134with an end 135 of the valve chest 111.

.The arrangement is such thatv when the pressure in either side of thehydraulic circuit, that is, in either of the pipes 24 or 25, exceeds apredetermined limit, the corre- `sponding`relief valve 125 or 126 isopened and the Huid is forced through pipe 134 into the end 135 of thevalve chest. Pressure is thus established behind the piston head 119causing the piston to move to the left until the piston head 118 hasmoved out of the port 114 and communication has been establishedtherethrough between the chambers 112 Vand 113. The two sides of thecircuit are thus promptly by-passed and vthe pressure in the h1 hpressure side. destroyed.:

This obviously rings the cross-head 16eto rest. .l his by-pass remainsopen until the piston as been returned to its normal position bymanipulating the stem 120 so that the cross-head remains at rest untilthe operator has corrected the trouble and `forced the stem 120 home. y'

`Various changema be made in the illustrative embodiment o the inventionhereinabove described, without departing from or sacricing any of theadvantages of the invention as defined in the appended claims.

I claim: v 1. The combination 'of a driven memtber, hydraulic meansincluding a reversibleow variable displacement pump for driving siidd`1s member, means for regulating pump placement, a spring connected atone end to said regulating means and operable thereon to reverse theflow of said pum and means controllediby movement of sai member -forshifting the other end of said spring linto either of two operatingositions.

2. The combination o al driven member,

hydraulic means including a reversible flow variable displacement pumpfor driving said member, means for regulating pump displacement,adjustable means for regulating the extent ol movement of saidregulating means, a spring connected at one end to said regulating meansand operable thereon to reverse the flow of said pump in eitherdirection, and means controlled by movement of said member for shiftingthe other end of said spring into either of two operating positions.

3. The combination of a driven member, hydraulic means including areversible flow, variable displacement pump for driving said member,means for regulating pump displacement, a spring connected at one end toto reverse the iow of said pump, means controlled by movement of saidmember for vsaid regulating means and operable thereon shifting 'the'other end of said spring into leasing said mechanism to complete theac-` tion of said regulating means.

' 5. In a hydraulic transmission for machine tools andthe like, thecombination of a variable displacement pump, a hydraulic circuit fledthereby, means for varying and controlling puinp displacement, and meansincluding a valve associated with said means for placing the oppositesides of said circuit in communication when said pump displacement issubstantially zero.

6. In a hydraulic transmission the comi bination of a variabledisplacement pump, a hydraulic motor, a Huid circuit connectin pump andmotor, means for varying and controlling pump displacement, and meansassociated with said last named means for short circuiting said circuitwhen said pump displacementI is substantially zero.

7. `In a hydraulic transmission the combination-of a variable strokepump, a hydraulic Amotor, a Huid circuit connecting pump 'and motor,short circuiting means therefor, means for controlling the pump stroke,and means for opening said short circuiting means when said controlmeans is set at zero pump stroke and for closing said short circuitingmeans when said control means is=shifted from zero pump stroke.

8. In a hydraulic transmission the combination of a variable strokepump, a hydraulic motor, a fluid circuit connecting pump and motor,short circuiting means therefor, means for controlling pump stroke,means for yieldably maintaining said short circuiting means effective,and means for rendering said short circuiting means ineffective Whensaid control means is shifted from zero stroke position.

9. In a hydraulic transmission the combination of a pump and motor, afluid circuit connecting them, short circuiting means` therefor, meanscontrolled by the pressure in said circuit for rendering said shortcircuiting means effective, and manual means for rendering said shortcircuiting means ineective.

l0. In a hydraulic transmission the combination of a pump and motor, afluid circuit connecting them, a valve controlled by the pressure offluid in said circuit for relieving the pressure therein, and manualmeans for resetting said valve.

11. In a hydraulic system the combination of a pressure conduit, a valvechest having a chamber communicating with said conduitl and an exhaustpassage, a valve normally closing said passage, a pressure relief valvealgemeen associated with said conduit, and means for delivering the uidwhich passes said relief valve into said valve chest to shift said rstnamed valve and open said passage.

12. lfn a hydraulic system the combination of a fluid circuit havinghigh and loW pressure sides, means including a valve for openl .ingcommunication between said sldes, and

means including a pressure controlled valve associated with said highpressure side for applying fluid pressure to said first named valve toopen said communication. v

13. ln a hydraulic transmission the combination of a Work circuit, meansfor forcing Huid through said circuit in either direction, a valve chesthaving a port adapted to communicate with both sides of said circuit tobreak the circuit, a member normally closing said port, a pressurecontrolled means associated with each side of said circuit, and meansassociated with said pressure controlled means through which fluidpressure is applied to said member to open said port when the pressurein either side of the circuit exceeds a predetermined degree.

In Witness whereof, I hereunto subscribe my name this 15th day ofSeptember, 1923.

WALTER FERRIS.

